Mono Documentation

Removes the invocation list of a Delegate from the invocation list of another delegate. [Edit]

public static Delegate Remove (Delegate source, Delegate value)

Parameters

source
The delegate from which to remove the invocation list of value. [Edit]
value
The delegate that supplies the invocation list to remove from source. [Edit]

Returns

Returns a new delegate, source, or null .
If source and value are not null , are not equal, and the invocation list of value is contained in the invocation list of source, returns a new delegate with the invocation list of value removed from the invocation list of source.
If the invocation lists of source and value are equal, returns null .
If the invocation list of value is not found in the invocation list of source, returns source.
The following table describes the value returned when source or value is null .
source value Return value
null null null
null non-null null
non-null null source
[Edit]

source	value	Return value
null	null	null
null	non-null	null
non-null	null	source

Remarks

The invocation list of value is required to be an exact match of a contiguous set of elements in the invocation list of source. If the invocation list of value occurs more than once in the invocation list of source, the last occurrence is removed. [Edit]

Example

The following example demonstrates the Delegate.Remove(Delegate, Delegate) method.

C# Example

using System;
class MyClass {
    public string InstanceMethod(string s) {
    return ("Instance String " + s);
    }
}
class MyClass2 {
    public string InstanceMethod2(string s) {
    return ("Instance String2 " + s);
    }
}
public delegate string DelegatedMethod(string s);

class TestClass {
    public static void WriteDelegate (string label, Delegate d) {
    Console.WriteLine("Invocation list targets for {0}:",label);
    foreach(Delegate x in d.GetInvocationList())
        Console.WriteLine("{0}",x.Target);
    }

    public static void Main() {
    MyClass myInstance = new MyClass();
    DelegatedMethod delInstance = new DelegatedMethod(myInstance.InstanceMethod);
    MyClass2 myInstance2 = new MyClass2();
    DelegatedMethod delInstance2 = new DelegatedMethod(myInstance2.InstanceMethod2);
    DelegatedMethod [] sourceArray = {delInstance, delInstance2, delInstance2, delInstance};
    DelegatedMethod [] remove1 = {delInstance};
    DelegatedMethod [] remove2 = {delInstance2, delInstance2};
    DelegatedMethod [] remove3 = {delInstance2, delInstance};
    DelegatedMethod [] remove4 = {delInstance, delInstance2};
    DelegatedMethod [] remove5 = {delInstance, delInstance};
    Delegate source = Delegate.Combine(sourceArray);
    // Display invocation list of source
    TestClass.WriteDelegate("source", source);
    //Test 1: value occurs in source twice.
    Delegate value1 = Delegate.Combine(remove1);
    Delegate result1 = Delegate.Remove(source, value1);
    TestClass.WriteDelegate("value1", value1);
    if (result1==null) {
        Console.WriteLine("removal test 1 result is null");
    } else {
        TestClass.WriteDelegate("result1", result1);
    }
    //Test 2: value matches the middle two elements of source.
    Delegate value2 = Delegate.Combine(remove2);
    Delegate result2 = Delegate.Remove(source, value2);
    TestClass.WriteDelegate("value2", value2);
    if (result2==null) {
        Console.WriteLine("removal test 2 result2 is null");
    } else {
        TestClass.WriteDelegate("result2", result2);
    }
    //Test 3: value matches the last two elements of source.
    Delegate value3 = Delegate.Combine(remove3);
    Delegate result3 = Delegate.Remove(source, value3);
    TestClass.WriteDelegate("value3", value3);
    if (result3==null) {
        Console.WriteLine("removal test 3 result3 is null");
    } else {
        TestClass.WriteDelegate("result3", result3);
    }
    //Test 4: value matches the first two elements of source.
    Delegate value4 = Delegate.Combine(remove4);
    Delegate result4 = Delegate.Remove(source, value4);
    TestClass.WriteDelegate("value4", value4);
    if (result4==null) {
        Console.WriteLine("removal test 4 result4 is null");
    } else {
        TestClass.WriteDelegate("result4", result4);
    }
    //Test 5: value does not occur in source.
    Delegate value5 = Delegate.Combine(remove5);
    Delegate result5 = Delegate.Remove(source, value5);
    TestClass.WriteDelegate("value5", value5);
    if (result5==null) {
        Console.WriteLine("removal test 5 result5 is null");
    } else {
        TestClass.WriteDelegate("result5", result5);
    }
    //Test 6: value exactly matches source.
    Delegate result6 = Delegate.Remove(source, source);
    TestClass.WriteDelegate("value=source", source);
    if (result6==null) {
        Console.WriteLine("removal test 6 result6 is null");
    } else {

        TestClass.WriteDelegate("result6", result6);
    }
}
}

The output is

Invocation list targets for source: MyClass MyClass2 MyClass2 MyClass Invocation list targets for value1: MyClass Invocation list targets for result1: MyClass MyClass2 MyClass2 Invocation list targets for value2: MyClass2 MyClass2 Invocation list targets for result2: MyClass MyClass Invocation list targets for value3: MyClass2 MyClass Invocation list targets for result3: MyClass MyClass2 Invocation list targets for value4: MyClass MyClass2 Invocation list targets for result4: MyClass2 MyClass Invocation list targets for value5: MyClass MyClass Invocation list targets for result5: MyClass MyClass2 MyClass2 MyClass Invocation list targets for value=source: MyClass MyClass2 MyClass2 MyClass removal test 6 result6 is null

Requirements

Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0

System.Delegate.Remove Method

Parameters

Returns

Remarks

Example

Requirements